1. Field of the Invention
The present invention generally relates to a magnetic head, and, more particularly, to a magnetic head used in reproducing magnetically recorded information from a magnetic recording medium such as a hard disk.
2. Description of the Related Art
A magnetic recording and reproducing device, such as a magnetic disk device, is widely employed as an external recording and reproducing device of a computer. Recently, as such a magnetic recording and reproducing device has drastically come to have a mass capacity, a magnetic recording medium has come to have a sharply increased recording density. Accordingly, there have been increasing needs for a magnetic head capable of providing a high performance. A magnetic head of a magnetoresistance type (an MR head) is drawing attention as a magnetic head satisfying these needs, since the MR head can provide a high-level output without depending on a speed of the magnetic recording medium. Such an MR head includes an MR head using a single-layer film, an MR head using a spin-valve film, and an MR head using a tunnel-effect film.
Especially, the MR head using the spin-valve film utilizing a huge magnetoresistance effect has recently been popular, while the MR head using the tunnel-effect film is being brought into practical use. These MR heads include a free magnetic layer as a structure thereof. As a magnetic recording and reproducing device has come to have a mass capacity, these MR heads have been further miniaturized. In order to provide these MR heads with a still higher capability under this circumstance, technologies have soon to be established, in which technologies a magnetic domain of the above-mentioned free magnetic layer is surely regulated.
Known as one of the above-mentioned technologies is a structure of an MR head of a spin-valve type, in which a magnetic-domain regulating film is connected to each side of a spin-valve film functioning as a magnetoresistance film. FIG. 1 shows a basic structure of a conventional spin-valve-type MR head 100. It is noted that a conductor lead-out layer and an upper insulating layer described hereinafter are not shown in FIG. 1.
In this spin-valve-type MR head 100, an insulating layer 101 is formed of such a material as alumina (Al2O3) so as to form a gap. A spin-valve film 103 (a magnetoresistance film) is formed on the insulating layer 101. A magnetic-domain regulating film 106 is also formed on the insulating layer 101 so as to flank the 103. This magnetic-domain regulating film 106 is referred to as a hard film 106 since the magnetic-domain regulating film 106 is formed of a hard-magnetic material consisting of such a material as a Co-group material. An underlying layer 105 formed generally of a Cr-group material is provided between the insulating layer 101 and the hard film 106 for the purpose of improving a crystallinity of the hard film 106.
For example, the above-mentioned spin-valve-type MR head 100 can be manufactured by steps shown in FIG. 2A to FIG. 2F. The manufacturing steps shown in FIG. 2A to FIG. 2F form the above-mentioned films one by one on the insulating layer 101 by using thin-film formation technologies including sputtering and etching so as to form a desired laminated structure. It is noted that FIG. 2A to FIG. 2F show only the left side of the spin-valve film 103, because both sides of the spin-valve film 103 are symmetrical.
FIG. 2A shows a step of forming the spin-valve film 103 on the insulating layer 101 composed of alumina (Al2O3). If the spin-valve film 103 has a regular-order laminated structure, the spin-valve film 103 has a free magnetic layer, a nonmagnetic layer, a pinned magnetic layer and an antiferromagnetic layer laminated in this order from the bottom; if the spin-valve film 103 has a reverse-order laminated structure, the spin-valve film 103 has an antiferromagnetic layer, a pinned magnetic layer, a nonmagnetic layer and a free magnetic layer laminated in this order from the bottom, though not shown in the figures. Besides, an underlying layer 102 is formed under the spin-valve film 103, i.e., between the insulating layer 101 and the spin-valve film 103. This underlying layer 102 is provided case by case so as to improve a crystallinity of the spin-valve film 103.
FIG. 2B shows a step of patterning the spin-valve film 103 and the underlying layer 102. In this step, the spin-valve film 103 and the underlying layer 102 are patterned into a shape corresponding to a track width (in the crosswise direction in FIG. 2A to FIG. 2F) of a magnetic recording medium. It is noted that the underlying layer 102 is not shown in FIG. 2C to FIG. 2F.
FIG. 2C shows a step of forming the underlying layer 105 for the hard film 106 that is to be formed in the next step. FIG. 2D shows a step of forming the hard film 106 on the underlying layer 105 so that the hard film 106 contacts each end of the spin-valve film 103.
FIG. 2E shows a step of forming a conductive lead-out layer 107 on the hard film 106. The conductive lead-out layer 107 is to be used to electrically take out a magnetoresistance change in the spin-valve film 103.
Finally, FIG. 2F shows a step of forming an insulating layer 109 on the spin-valve film 103 and the conductive lead-out layer 107. The heretofore-mentioned steps shown in FIG. 2A to FIG. 2F form the conventional spin-valve-type MR head 100.
In the above-described spin-valve-type MR head 100, the underlying layer 102 is on the insulating layer 101, and the spin-valve film 103 is on the underlying layer 102; that is, the upper surface of the insulating layer 101 and the bottom surface of the underlying layer 102 are in the same plane.
However, there are two problems regarding a regulation of a magnetic domain of the above-mentioned free magnetic layer of the spin-valve film 103.
A description will be given, with reference to FIG. 1, FIG. 3A, FIG. 3B and FIG. 4, of the first problem. FIG. 3A and FIG. 3B show magnetic characteristics of the hard film 106. Specifically, FIG. 3A shows a magnetic characteristic of the hard film 106 in a territory TER-A shown in FIG. 1, and FIG. 3B shows a magnetic characteristic of the hard film 106 in a territory TER-B shown in FIG. 1.
The magnetic characteristic of the hard film 106 shown in FIG. 3A is good, marking a coercive force of 1230 Oe and a squareness ratio of 0.86, because the hard film 106 is formed on the underlying layer 105 composed of a Cr-group material provided on the insulating layer 101.
However, a part of the spin-valve film 103, the antiferromagnetic layer for example, remains under the joining part between the spin-valve film 103 and the hard film 106 in the territory TER-B. Therefore, there is a lamination, around the joint part in the territory TER-B, of the underlying layer 105 formed on the antiferromagnetic layer and the hard film 106 formed on this underlying layer 105.
Additionally, in the territory TER-B, the underlying layer 105 for the hard film 106 tends to be formed thinner than in the territory TER-A. Therefore, the underlying layer 105 does not function sufficiently in improving a crystallinity of the hard film 106. In other words, since the underlying layer 105 is formed on the spin-valve film 103 that has a predetermined crystallinity, the spin-valve film 103 puts a bad influence on the crystallinity-improvement function of the underlying layer 105.
The inventors of the present invention have confirmed that forming the underlying layer 105 on the antiferromagnetic layer of the spin-valve film 103 deteriorates the crystallinity-improvement function of the underlying layer 105. Thus, when the hard film 106 is formed on the underlying layer 105 having such a deteriorated crystallinity-improvement function, the hard film 106 naturally comes to have a deteriorated crystallinity. Accordingly, the hard film 106 comes to have a deteriorated magnetic characteristic as shown in FIG. 3B, marking a coercive force of 330 Oe and a squareness ratio of 0.80.
FIG. 4 shows, by using an X-ray diffraction, the hard film 106 having a deteriorated crystallinity. In FIG. 4, there occur not only a PEAK-1 based on the spin-valve film 103 but also a PEAK-2 based on a (001) surface of Co. This PEAK-2 indicates that there exists a crystal grain having the c-axis of Co composing the hard film 106 aligned in the direction of thickness thereof; therefore a deteriorated coercive force and a deteriorated squareness ratio can be confirmed also from FIG. 4.
The above-mentioned territory TER-B is a part at which the hard film 106 connects with the spin-valve film 103, and is important in regulating magnetic domains by applying a bias magnetic field to the free magnetic layer. However, the above-mentioned conventional spin-valve-type MR head 100 has the first problem that this connection part tends to have a deteriorated characteristic.
Further, a description will be given of the second problem of the above-mentioned spin-valve-type MR head 100. In order to further increase the output level, the spin-valve-type MR head 100 is made to have still thinner films. Therefore, the spin-valve film 103 and the free magnetic layer composing the spin-valve film 103 are made to be thinner and thinner. Accordingly, the hard film 106 formed on each side of the spin-valve film 103 is made to be thinner.
FIG. 5A is a magnified view showing a state of the spin-valve-type MR head 100 having thinner films, with the spin-valve film 103 employing the reverse-order laminated structure. FIG. 5B is a magnified view showing a state of the spin-valve-type MR head 100 having thinner films, with the spin-valve film 103 employing the regular-order laminated structure.
As the spin-valve-type MR head 100 has thinner films, the center plane of a free magnetic layer 103FR is shifted upward in the direction of thickness so as to be formed HT1 above the upper surface of the hard film 106, in the case of the reverse-order laminated structure shown in FIG. 5A. To the contrary, in the case of the regular-order laminated structure shown in FIG. 5B, the center plane of the free magnetic layer 103FR is shifted downward in the direction of thickness so as to be formed HT2 below the under surface of the hard film 106.
When the center plane of the free magnetic layer 103FR is shifted in position in the direction of thickness from the hard film 106, there occurs the second problem that the hard film 106 cannot sufficiently regulate a magnetic domain of the free magnetic layer 103FR.
In addition, with respect to the above-mentioned second problem, Japanese Laid-Open Patent Application No. 10-124823, Japanese Laid-Open Patent Application No. 10-154314 and Japanese Laid-Open Patent Application No. 2000-132817, for example, proposes a technology in which the antiferromagnetic layer of the spin-valve film is left under the hard film so as to raise the bottom of the hard film, regarding the above-described spin-valve-type MR head 100 having the spin-valve film 103 employing the reverse-order laminated structure shown in FIG. 5A.
FIG. 6A and FIG. 6B illustrate such a conventional technology of raising the bottom of the hard film. FIG. 6A illustrates a part of an MR head in which a Cr-group alloy is used as the underlying layer 105 (for the hard film) formed on the antiferromagnetic layer left as a part of the spin-valve film. FIG. 6B illustrates a part of an MR head in which a lamination of a Ta-group alloy and a Cr-group alloy is used as the underlying layer 105 formed on the antiferromagnetic layer left as a part of the spin-valve film.
Elements in FIG. 6A and FIG. 6B are referenced by the same reference marks as in FIG. 2A to FIG. 2F illustrating steps of manufacturing a conventional MR head. Additionally, with respect to the spin-valve film 103, the antiferromagnetic layer is indicated by a reference mark 103-1, and the pinned magnetic layer, the nonmagnetic layer and the free magnetic layer are collectively indicated by a reference mark 103-2. Further, in FIG. 6B, the two layers of the Ta-group alloy and the Cr-group alloy in the lamination are distinctively indicated by reference marks 105-1 and 105-2.
FIG. 7 shows a result of comparing a conventional general MR head that does not have the antiferromagnetic layer formed under the underlying layer 105 as shown in FIG. 2F, with the MR heads each having the underlying layer 105 formed on the antiferromagnetic layer 103-1 shown in FIG. 6A and FIG. 6B.
In FIG. 7, the axis of abscissas indicates a head output, and the axis of ordinates indicates a Barkhausen proportion defective. In FIG. 7, an MR head is regarded as more preferable as the head output becomes high and the Barkhausen proportion defective becomes low. Besides, criterion values in both the axis of abscissas and the axis of ordinates are 1.00, according to a plurality of tests in which data processes are performed by using the conventional general MR head. Accordingly, when the head output becomes higher than 1, the head output can be regarded as improved. Also, when the Barkhausen proportion defective becomes lower than 1, the Barkhausen proportion defective can be regarded as improved.
However, as for the MR head shown in FIG. 6A, substantially no improvement can be recognized regarding the head output, and the Barkhausen proportion defective is prone to increase, as indicated by a white square in a circle A shown in FIG. 7. Therefrom, it can be understood that a highly sensitive MR head cannot be formed simply by raising the bottom of the hard film 106 by using the antiferromagnetic layer 103-1 so as to arrange the hard film 106 at a position corresponding to the free magnetic layer.
Additionally, the hard film 106 of the MR head shown in FIG. 6A comes to have a deteriorated magnetic characteristic, as in the case shown in FIG. 3B.
FIG. 6B, as mentioned above, shows a case in which the underlying layer 105 has two layers of a generally used Cr-group underlying layer and a Ta-group underlying layer. That is, in FIG. 6B, the underlying layer 105-2 (Cr) is formed on the underlying layer 105-1 (Ta) so as to together form the underlying layer 105. As indicated by a white triangle in a circle B in FIG. 7, regarding the MR head shown in FIG. 6B, although an improvement can be recognized regarding the head output, substantially no improvement can be found regarding the Barkhausen proportion defective.
In the MR heads shown in FIG. 6A and FIG. 6B, since the antiferromagnetic layer 103-1 exists under the underlying layer 105, the hard film 106 can be effectively positioned at the same height as the free magnetic layer. However, as described above, the antiferromagnetic layer 103-1 deteriorates the crystallinity of the underlying layer 105 formed thereon. Consequently, a preferable MR head cannot be formed.
As described heretofore, when simply using the antiferromagnetic layer to raise the bottom of the hard film in an attempt to solve the above-mentioned second problem, a highly sensitive MR head still cannot be achieved due to the above-mentioned first problem.
Accordingly, the spin-valve-type MR head 100 having the above-mentioned first and second problems causes a problem that the spin-valve-type MR head 100 cannot detect a signal magnetic field from a magnetic recording medium with high sensitivity.
It is a general object of the present invention to provide an improved and useful magnetic head of a magnetoresistance type in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a magnetic head of a magnetoresistance type which head has a magnetic-domain regulating film possessing an excellent magnetic characteristic arranged in an optimal position.
In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a magnetic head of a magnetoresistance type, the magnetic head comprising:
a magnetoresistance film;
an underlying layer formed on each of both sides of the magnetoresistance film, the underlying layer having a laminated structure of a tungsten-(W)-group metal layer formed on a tantalum-(Ta)-group metal layer; and
a magnetic-domain regulating film formed on the underlying layer so as to regulate a magnetic domain of the magnetoresistance film.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the laminated structure may further include a chromium-(Cr)-group metal layer formed on the tungsten-(W)-group metal layer.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the tungsten-(W)-group metal layer may be a layer alloyed with at least one selected from a group consisting of titanium (Ti) and vanadium (V).
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the chromium-(Cr)-group metal layer may be a layer alloyed with at least one selected from a group consisting of molybdenum (Mo), vanadium (V) and tungsten (W).
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the tungsten-(W)-group metal layer may be 1.7 to 10 nm in thickness.
According to the present invention, a magnetic head of a magnetoresistance type can have a magnetic-domain regulating film having good crystal conditions and excellent magnetic characteristics.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic head of a magnetoresistance type, the magnetic head comprising:
a magnetoresistance film;
an underlying layer formed on each of both sides of the magnetoresistance film; and
a magnetic-domain regulating film formed on the underlying layer so as to regulate a magnetic domain of a free magnetic layer in the magnetoresistance film,
wherein the underlying layer is formed so thick as to arrange the magnetic-domain regulating film at a position corresponding to the free magnetic layer.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic head of a magnetoresistance type, the magnetic head comprising:
a magnetoresistance film;
a nonmagnetic layer formed on each of both sides of the magnetoresistance film;
an underlying layer formed on the nonmagnetic layer; and
a magnetic-domain regulating film formed on the underlying layer so as to regulate a magnetic domain of a free magnetic layer in the magnetoresistance film,
wherein the nonmagnetic layer is used to arrange the magnetic-domain regulating film at a position corresponding to the free magnetic layer.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic head of a magnetoresistance type, the magnetic head comprising:
an insulating layer;
a magnetoresistance film formed on the insulating layer;
an underlying layer formed on each of both sides of the magnetoresistance film; and
a magnetic-domain regulating film formed on the underlying layer so as to regulate a magnetic domain of a free magnetic layer in the magnetoresistance film,
wherein a part of the insulating layer under the underlying layer is formed lower than the other parts of the insulating layer so as to arrange the magnetic-domain regulating film at a position corresponding to the free magnetic layer.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic head of a magnetoresistance type, the magnetic head comprising:
a magnetoresistance film;
an underlying layer formed on each of both sides of the magnetoresistance film; and
a magnetic-domain regulating film formed on the underlying layer so as to regulate a magnetic domain of a free magnetic layer in the magnetoresistance film,
wherein a center plane of the free magnetic layer in the direction of thickness is positioned within a range from a position corresponding to a center plane of the magnetic-domain regulating film to a position higher by 25% of a thickness of the magnetic-domain regulating film.
According to the present invention, since the magnetic-domain regulating film is arranged at an optimal position corresponding to the free magnetic layer so as to regulate a magnetic domain thereof, the magnetic head of the magnetoresistance type can provide an effective magnetic-domain regulation.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the underlying layer may preferably have a laminated structure of a tungsten-(W)-group metal layer formed on a tantalum-(Ta)-group metal layer.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the laminated structure may preferably further include a chromium-(Cr)-group metal layer formed on the tungsten-(W)-group metal layer.
According to the present invention, the magnetic-domain regulating film arranged at an optimal position can have excellent magnetic characteristics; therefore, the magnetic head of the magnetoresistance type can provide a more effective magnetic-domain regulation.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic head of a magnetoresistance type, the magnetic head comprising:
a first underlying layer;
a magnetoresistance film formed on the first underlying layer;
a second underlying layer formed on each of both sides of the magnetoresistance film; and
a magnetic-domain regulating film formed on the second underlying layer so as to regulate a magnetic domain of a free magnetic layer in the magnetoresistance film,
wherein the first underlying layer and the second underlying layer are so formed as to arrange the magnetic-domain regulating film at a position corresponding to the free magnetic layer.
Additionally, the magnetic head of the magnetoresistance type according to the present invention may further comprise a nonmagnetic layer formed between the first underlying layer and the second underlying layer so as to be used to arrange the magnetic-domain regulating film at the position corresponding to the free magnetic layer.
According to the present invention, since the magnetic-domain regulating film is arranged at an optimal position corresponding to the free magnetic layer so as to regulate a magnetic domain thereof, the magnetic head of the magnetoresistance type can provide an effective magnetic-domain regulation.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the second underlying layer may have a laminated structure of a tungsten-(W)-group metal layer formed on a tantalum-(Ta)-group metal layer.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the tungsten-(W)-group metal layer may be a layer alloyed with at least one selected from a group consisting of titanium (Ti) and vanadium (V).
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the laminated structure may further include a chromium-(Cr)-group metal layer formed on the tungsten-(W)-group metal layer.
According to the present invention, the magnetic-domain regulating film arranged at an optimal position can have excellent magnetic characteristics; therefore, the magnetic head of the magnetoresistance type can provide a more effective magnetic-domain regulation.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic head of a magnetoresistance type, the magnetic head comprising:
a magnetoresistance film detecting a magnetic field;
a residual film formed of a part of a layer composing the magnetoresistance film left on each of both sides thereof;
an underlying layer formed on the residual film, the underlying layer having a laminated structure of a tungsten-(W)-group metal layer formed on a tantalum-(Ta)-group metal layer; and
a magnetic-domain regulating film formed on the underlying layer so as to regulate a magnetic domain of a free magnetic layer in the magnetoresistance film.
According to the present invention, by using a part of a layer composing the magnetoresistance film, the magnetic-domain regulating film can be arranged at an optimal position corresponding to the free magnetic layer so as to regulate a magnetic domain thereof. Therefore, the magnetic head according to the present invention can provide an effective magnetic-domain regulation.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the laminated structure may further include a chromium-(Cr)-group metal layer formed on the tungsten-(W)-group metal layer.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the tungsten-(W)-group metal layer may be a layer alloyed with at least one selected from a group consisting of titanium (Ti) and vanadium (V).
According to the present invention, a magnetic head of a magnetoresistance type can have a magnetic-domain regulating film having good crystal conditions and excellent magnetic characteristics.
Additionally, in the magnetic head of the magnetoresistance type according to the present invention, the magnetoresistance film may be a spin-valve film having a reverse-order laminated structure, and the residual film may be an antiferromagnetic layer of the spin-valve film.
According to the present invention, the antiferromagnetic layer of the spin-valve film can be efficiently used to raise the bottom of the hard film.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic reproducing device for reproducing magnetic information from a magnetic recording medium, the device comprising:
a magnetic head of a magnetoresistance type, the magnetic head including:
a magnetoresistance film;
an underlying layer formed on each of both sides of the magnetoresistance film, the underlying layer having a laminated structure of a tungsten-(W)-group metal layer formed on a tantalum-(Ta)-group metal layer; and
a magnetic-domain regulating film formed on the underlying layer so as to regulate a magnetic domain of the magnetoresistance film.
In order to achieve the above-mentioned objects, there is also provided according to another aspect of the present invention a magnetic reproducing device for reproducing magnetic information from a magnetic recording medium, the device comprising:
a magnetic head of a magnetoresistance type, the magnetic head including:
a magnetoresistance film;
an underlying layer formed on each of both sides of the magnetoresistance film; and
a magnetic-domain regulating film formed on the underlying layer so as to regulate a magnetic domain of a free magnetic layer in the magnetoresistance film,
wherein the underlying layer is formed so thick as to arrange the magnetic-domain regulating film at a position corresponding to the free magnetic layer.
According to the present invention, the magnetic reproducing device can reproduce magnetic information with high sensitivity.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.